- Close races with signals and other AST's being triggered while we are in

  the process of exiting the kernel.  The ast() function now loops as long
  as the PS_ASTPENDING or PS_NEEDRESCHED flags are set.  It returns with
  preemption disabled so that any further AST's that arrive via an
  interrupt will be delayed until the low-level MD code returns to user
  mode.
- Use u_int's to store the tick counts for profiling purposes so that we
  do not need sched_lock just to read p_sticks.  This also closes a
  problem where the call to addupc_task() could screw up the arithmetic
  due to non-atomic reads of p_sticks.
- Axe need_proftick(), aston(), astoff(), astpending(), need_resched(),
  clear_resched(), and resched_wanted() in favor of direct bit operations
  on p_sflag.
- Fix up locking with sched_lock some.  In addupc_intr(), use sched_lock
  to ensure pr_addr and pr_ticks are updated atomically with setting
  PS_OWEUPC.  In ast() we clear pr_ticks atomically with clearing
  PS_OWEUPC.  We also do not grab the lock just to test a flag.
- Simplify the handling of Giant in ast() slightly.

Reviewed by:	bde (mostly)

1 files changed, 3 insertions, 3 deletions

diff --git a/sys/kern/ksched.c b/sys/kern/ksched.c
index c7f746a..c7b6dd3 100644
--- a/sys/kern/ksched.c
+++ b/sys/kern/ksched.c
@@ -176,7 +176,7 @@ int ksched_setscheduler(register_t *ret, struct ksched *ksched,
 
 			mtx_lock_spin(&sched_lock);
 			rtp_to_pri(&rtp, &p->p_pri);
-			need_resched(p);
+			p->p_sflag |= PS_NEEDRESCHED;
 			mtx_unlock_spin(&sched_lock);
 		}
 		else
@@ -198,7 +198,7 @@ int ksched_setscheduler(register_t *ret, struct ksched *ksched,
 			 *     on the scheduling code: You must leave the
 			 *     scheduling info alone.
 			 */
-			need_resched(p);
+			p->p_sflag |= PS_NEEDRESCHED;
 			mtx_unlock_spin(&sched_lock);
 		}
 		break;
@@ -217,7 +217,7 @@ int ksched_getscheduler(register_t *ret, struct ksched *ksched, struct proc *p)
 int ksched_yield(register_t *ret, struct ksched *ksched)
 {
 	mtx_lock_spin(&sched_lock);
-	need_resched(curproc);
+	curproc->p_sflag |= PS_NEEDRESCHED;
 	mtx_unlock_spin(&sched_lock);
 	return 0;
 }